1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device using a monocrystalline silicon carbide substrate.
2. Description of the Related Arts
A conventional power semiconductor device (power semiconductor device) has been manufactured by using a monocrystalline silicon substrate. The progress of design and manufacturing techniques of elements has reduced resistance (on-resistance) at the time of applying current while keeping a high breakdown voltage to realize low loss. However, the breakdown voltage and on-resistance have a trade-off relation in which they are determined on the basis of a band gap of the material of a substrate, and thus, there is a limit to improvement of performance as long as the conventional silicon is used. Therefore, as a material in place of silicon, a wide-gap semiconductor such as silicon carbide and gallium nitride has attracted attention. Use of the wide-gap semiconductor can realize a high-performance power semiconductor device as compared to use of silicon. In particular, development of a power semiconductor device using silicon carbide has been increasing. The first reason is that the high quality and large diameter of a monocrystalline silicon carbide substrate have been realized, and it is relatively easy to obtain a substrate necessary for manufacturing a semiconductor device. The second reason is that n-type and p-type conductive areas can be easily formed on a monocrystalline silicon carbide substrate by epitaxial growth and ion implantation, and a film primarily including silicon dioxide can be formed thereon by thermal oxidation. Accordingly, there has been a possibility that various power semiconductor devices can be manufactured. As a switching element, there have been studied, so far, a BJT (Bipolar Junction Transistor), in addition to a unipolar element such as an MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and a JFET (Junction Field Effect Transistor). Further, as a rectifying device, a p-n junction diode and a Schottky barrier diode have been developed. In particular, for high breakdown voltage, a diode element called JBS (Junction Barrier Schottky) obtained by combining a p-n junction diode and a Schottky barrier diode has been developed.